That can be a hard question to answer, but if there are multiple games you are looking forward to playing on the PS3, then I say sure, but if you are only wanting it for 1 game, then it may not be a good idea. In the end it all depends if you think it`s worth it.
Well The Last of Us has received something like 30 perfect score reviews so far. Naughty Dog is an elite studio that makes great games. But there are also a lot of other great games you can play on PS3 too.